The present invention relates to a drive transmission unit.
In many applications motion transmission units are required wherein, first of all, the power output shaft is inclined with respect to the input shaft where the power is generated.
This is the case, for example, with marine applications, where the output shaft is conveniently horizontal whilst the output shaft or propeller shaft is inclined.
In addition, the direction of rotation of the output shaft must be selectively provided both in the same direction as and the opposite direction with respect to the direction of rotation of the input shaft because of the need to provide a reverse gear and for special applications.
In fact, in marine applications, it often occurs that the boat or craft is equipped with two engines which individually actuate one propeller each.
In this case to avoid problems of craft balancing, it is appropriate for the propellers in use to be counter-directionally rotating, thereby the transmission means which is interposed between the engine and the propeller that is the transmission drive, is for one propeller shaft arranged to turn in one direction and for the second propeller shaft to turn in the opposite direction.
In practice, in the situation of normal travel, one of the two drive transmissions is operable in a condition that is defined herein as "forward gear", whilst the other of the two drive transmissions is operable in a condition that is defined herein as "reverse gear".
With drive transmission units utilized heretofore, the performance and operating conditions respectively in "forward gear" and "reverse gear" are not the same owing indeed to the particular combination of gears that they contain.
This means that one transmission unit drive works in favourable conditions when in "forward gear" whilst its performance is notably inferior when it is operated in "reverse gear".
This depends on the fact that in one of the two directions of movement gears are employed which are different from those utilized in the other direction of movement.